The present invention relates to a system for treating water for drinking using reverse osmosis membrane separation and, more particularly, to a flow control module for use in such a system whereby replacement may be easily effected.
Replaceable reverse osmosis (RO) filter cartridges have been used for many years for the purification of drinking water. Systems utilizing RO membrane filter cartridges have been made in many sizes and have often been combined with other types of pre-RO and post-RO filter elements of different types connected in series to provide for the comprehensive removal of contaminants. A typical system which has evolved in the prior art comprises a multi-cartridge system including three serially connected filter units, all of which are contained in similar filter housings that are demountably attached to a common header for handling the various flow distribution lines and connections. It is also typical to provide pure water storage in an interconnected reservoir so that a larger on-demand volume of filtered water may be provided than would normally be available directly from a typical RO filter. In addition to a conventional faucet valve operated by the user to obtain filtered water, a typical system also includes interior valving and flow controls to provide automatic feed water shutoff when the reservoir is fall, back pressure control on the RO membrane unit to maintain a proper flow balance, and a check valve to prevent reverse flow of pure water through the RO filter unit. All of these various flow passages and controls result in fairly complex flow patterns and valve arrangements.
Attempts have been made in the prior art to provide common headers for all of the filter elements in a multi-element system. Also, multi-function or modular valve arrangements are shown in the prior art. The use of unitary headers has not adequately addressed the problem of connecting thereto the various flow control devices. Conversely, the use of modular flow control units has typically required complex piping arrangements with many separate connections. In either event, the flow control components may periodically require servicing or replacement and access to the various components is typically difficult and time consuming.
In accordance with the present invention, a semi-permeable membrane filter system, which may include pre-RO and post-RO filter units, utilizes a manifold and a single control module that includes all of the basic valve and flow control components for the system (with the exception of the user on-off faucet control). The control module is readily accessible for easy servicing and replacement of the module. The manifold is operatively connected to the membrane filter unit and includes a supply flow path for directing a pressurized flow of raw water to the membrane filter unit, a permeate flow path for directing membrane permeate (pure water) to a pressurized storage tank, and a brine flow path for directing membrane concentrate to a drain. The control module includes a demountable housing that is attached directly to the manifold and entirely enclosing therein a pressure responsive supply flow shutoff valve, a brine flow control valve, and a permeate flow check valve, as well as the respective interconnections between the manifold and the several valves. The membrane filter unit preferably comprises a reverse osmosis filter cartridge that is removably contained in an open-ended filter housing. The manifold overlies the filter unit and includes a downwardly depending threaded boss to which the threaded open end of the filter housing is attached. The control module mounts to the manifold directly above the threaded boss, and the control housing includes a supply flow outlet in direct fluid connection with a supply flow opening in the manifold boss, a permeate flow inlet in direct fluid communication with a permeate flow opening in the manifold boss, and a brine flow inlet in direct fluid communication with a brine flow opening in the manifold boss.
In the preferred embodiment, the manifold boss defines a cylindrical outer sleeve, and there is further included a cylindrical intermediate sleeve that is concentric with the outer sleeve and defines therewith a first annular space, and a cylindrical inner sleeve that is concentric with said intermediate sleeve and defines therewith a second annular space. The brine flow opening communicates with the first annular space, the supply flow opening communicates with the second annular space, and the permeate flow opening is defined by the interior of the inner sleeve. In the preferred embodiment, the filter cartridge includes a membrane that is wrapped on a hollow tubular core and covered externally with an outer impervious layer. The membrane is disposed with open upper and lower ends and the cartridge is contained in the filter housing to define an open space between the outer layer, the open lower end of the cartridge and the interior of the housing. The first annular space in the boss communicates with said open space, the second annular space communicates with the open upper end of the membrane, and the interior of the inner sleeve communicates with the hollow tubular core of the RO element. First sealing means prevents a cross flow of liquid between the first annular space and the second annular space, and a second sealing means prevents a cross flow of liquid between the second annular space and the interior of the inner sleeve.
In the preferred embodiment, the control module housing comprises a molded plastic body having integrally molded in the body the supply flow interconnection, the permeate flow interconnection, the brine flow interconnection, and a recess for the shutoff valve; and means are provided for mounting the module body to the manifold to simultaneously effect the respective interconnections.